Invariant-mass spectroscopy of $^{14}$O excited states

TL;DR

This study combines experimental neutron-knockout reactions and theoretical Shell Model Embedded in the Continuum calculations to investigate and assign properties to excited states of $^{14}$O, revealing complex decay behaviors and near-degenerate states.

Contribution

It provides new experimental data and theoretical analysis for $^{14}$O excited states, including spin, parity, and decay pathways, with novel insights into sequential decay interference effects.

Findings

Identification of all excited states below 8 MeV with assigned spins and parities.

Observation of near degeneracy between the second 2$^{+}$ and third 0$^{+}$ states.

Discovery of interference effects in sequential 2$p$ decay involving degenerate $^{13}$N states.

Abstract

Excited states in $^{14}$O have been investigated both experimentally and theoretically. Experimentally, these states were produced via neutron-knockout reactions with a fast $^{15}$O beam and the invariant-mass technique was employed to isolate the 1$p$ and 2$p$ decay channels and determine their branching ratios. The spectrum of excited states was also calculated with the Shell Model Embedded in the Continuum that treats bound and scattering states in a unified model. By comparing energies, widths and decay branching patterns, spin and parity assignments for all experimentally observed levels below 8 MeV are made. This includes the location of the second 2$^{+}$ state that we find is in near degeneracy with the third 0$^{+}$ state. An interesting case of sequential 2$p$ decay through a pair of degenerate $^{13}$N excited states with opposite parities was found where the interference between the two sequential decay pathways produces an unusual relative-angle distribution between the emitted protons.